The Wealth of Nations by Part 2 Chapter 5 Page 8

productive labourers. Their labour, when properly directed, fixes and realizes itself in the subject or vendible commodity upon which it is bestowed, and generally adds to its price the value at least of their own maintenance and consumption. The profits of the farmer, of the manufacturer, of the merchant, and retailer, are all drawn from the price of the goods which the two first produce, and the two last buy and sell. Equal capitals, however, employed in each of those four different ways, will immediately put into motion very different quantities of productive labour, and augment, too, in very different proportions the value of the annual produce of the land and labour of the society to which they belong.

The capital of the retailer replaces, together with its profits, that of the merchant of whom he purchases goods, and